fs/char_dev.c

   1 /*
   2  *  linux/fs/char_dev.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/config.h>
   8 #include <linux/init.h>
   9 #include <linux/fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/string.h>
  12
  13 #include <linux/major.h>
  14 #include <linux/errno.h>
  15 #include <linux/module.h>
  16 #include <linux/smp_lock.h>
  17 #include <linux/devfs_fs_kernel.h>
  18
  19 #include <linux/kobject.h>
  20 #include <linux/kobj_map.h>
  21 #include <linux/cdev.h>
  22
  23 #ifdef CONFIG_KMOD
  24 #include <linux/kmod.h>
  25 #endif
  26
  27 static struct kobj_map *cdev_map;
  28
  29 #define MAX_PROBE_HASH 255      /* random */
  30
  31 static DECLARE_MUTEX(chrdevs_lock);
  32
  33 static struct char_device_struct {
  34         struct char_device_struct *next;
  35         unsigned int major;
  36         unsigned int baseminor;
  37         int minorct;
  38         char name[64];
  39         struct file_operations *fops;
  40         struct cdev *cdev;              /* will die */
  41 } *chrdevs[MAX_PROBE_HASH];
  42
  43 /* index in the above */
  44 static inline int major_to_index(int major)
  45 {
  46         return major % MAX_PROBE_HASH;
  47 }
  48
  49 struct chrdev_info {
  50         int index;
  51         struct char_device_struct *cd;
  52 };
  53
  54 void *get_next_chrdev(void *dev)
  55 {
  56         struct chrdev_info *info;
  57
  58         if (dev == NULL) {
  59                 info = kmalloc(sizeof(*info), GFP_KERNEL);
  60                 if (!info)
  61                         goto out;
  62                 info->index=0;
  63                 info->cd = chrdevs[info->index];
  64                 if (info->cd)
  65                         goto out;
  66         } else {
  67                 info = dev;
  68         }
  69
  70         while (info->index < ARRAY_SIZE(chrdevs)) {
  71                 if (info->cd)
  72                         info->cd = info->cd->next;
  73                 if (info->cd)
  74                         goto out;
  75                 /*
  76                  * No devices on this chain, move to the next
  77                  */
  78                 info->index++;
  79                 info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
  80                         chrdevs[info->index] : NULL;
  81                 if (info->cd)
  82                         goto out;
  83         }
  84
  85 out:
  86         return info;
  87 }
  88
  89 void *acquire_chrdev_list(void)
  90 {
  91         down(&chrdevs_lock);
  92         return get_next_chrdev(NULL);
  93 }
  94
  95 void release_chrdev_list(void *dev)
  96 {
  97         up(&chrdevs_lock);
  98         kfree(dev);
  99 }
 100
 101
 102 int count_chrdev_list(void)
 103 {
 104         struct char_device_struct *cd;
 105         int i, count;
 106
 107         count = 0;
 108
 109         for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
 110                 for (cd = chrdevs[i]; cd; cd = cd->next)
 111                         count++;
 112         }
 113
 114         return count;
 115 }
 116
 117 int get_chrdev_info(void *dev, int *major, char **name)
 118 {
 119         struct chrdev_info *info = dev;
 120
 121         if (info->cd == NULL)
 122                 return 1;
 123
 124         *major = info->cd->major;
 125         *name = info->cd->name;
 126         return 0;
 127 }
 128
 129 /*
 130  * Register a single major with a specified minor range.
 131  *
 132  * If major == 0 this functions will dynamically allocate a major and return
 133  * its number.
 134  *
 135  * If major > 0 this function will attempt to reserve the passed range of
 136  * minors and will return zero on success.
 137  *
 138  * Returns a -ve errno on failure.
 139  */
 140 static struct char_device_struct *
 141 __register_chrdev_region(unsigned int major, unsigned int baseminor,
 142                            int minorct, const char *name)
 143 {
 144         struct char_device_struct *cd, **cp;
 145         int ret = 0;
 146         int i;
 147
 148         cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
 149         if (cd == NULL)
 150                 return ERR_PTR(-ENOMEM);
 151
 152         memset(cd, 0, sizeof(struct char_device_struct));
 153
 154         down(&chrdevs_lock);
 155
 156         /* temporary */
 157         if (major == 0) {
 158                 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
 159                         if (chrdevs[i] == NULL)
 160                                 break;
 161                 }
 162
 163                 if (i == 0) {
 164                         ret = -EBUSY;
 165                         goto out;
 166                 }
 167                 major = i;
 168                 ret = major;
 169         }
 170
 171         cd->major = major;
 172         cd->baseminor = baseminor;
 173         cd->minorct = minorct;
 174         strncpy(cd->name,name, 64);
 175
 176         i = major_to_index(major);
 177
 178         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 179                 if ((*cp)->major > major ||
 180                     ((*cp)->major == major && (*cp)->baseminor >= baseminor))
 181                         break;
 182         if (*cp && (*cp)->major == major &&
 183             (*cp)->baseminor < baseminor + minorct) {
 184                 ret = -EBUSY;
 185                 goto out;
 186         }
 187         cd->next = *cp;
 188         *cp = cd;
 189         up(&chrdevs_lock);
 190         return cd;
 191 out:
 192         up(&chrdevs_lock);
 193         kfree(cd);
 194         return ERR_PTR(ret);
 195 }
 196
 197 static struct char_device_struct *
 198 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 199 {
 200         struct char_device_struct *cd = NULL, **cp;
 201         int i = major_to_index(major);
 202
 203         down(&chrdevs_lock);
 204         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 205                 if ((*cp)->major == major &&
 206                     (*cp)->baseminor == baseminor &&
 207                     (*cp)->minorct == minorct)
 208                         break;
 209         if (*cp) {
 210                 cd = *cp;
 211                 *cp = cd->next;
 212         }
 213         up(&chrdevs_lock);
 214         return cd;
 215 }
 216
 217 int register_chrdev_region(dev_t from, unsigned count, const char *name)
 218 {
 219         struct char_device_struct *cd;
 220         dev_t to = from + count;
 221         dev_t n, next;
 222
 223         for (n = from; n < to; n = next) {
 224                 next = MKDEV(MAJOR(n)+1, 0);
 225                 if (next > to)
 226                         next = to;
 227                 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
 228                                next - n, name);
 229                 if (IS_ERR(cd))
 230                         goto fail;
 231         }
 232         return 0;
 233 fail:
 234         to = n;
 235         for (n = from; n < to; n = next) {
 236                 next = MKDEV(MAJOR(n)+1, 0);
 237                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 238         }
 239         return PTR_ERR(cd);
 240 }
 241
 242 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
 243                         const char *name)
 244 {
 245         struct char_device_struct *cd;
 246         cd = __register_chrdev_region(0, baseminor, count, name);
 247         if (IS_ERR(cd))
 248                 return PTR_ERR(cd);
 249         *dev = MKDEV(cd->major, cd->baseminor);
 250         return 0;
 251 }
 252
 253 int register_chrdev(unsigned int major, const char *name,
 254                     struct file_operations *fops)
 255 {
 256         struct char_device_struct *cd;
 257         struct cdev *cdev;
 258         char *s;
 259         int err = -ENOMEM;
 260
 261         cd = __register_chrdev_region(major, 0, 256, name);
 262         if (IS_ERR(cd))
 263                 return PTR_ERR(cd);
 264
 265         cdev = cdev_alloc();
 266         if (!cdev)
 267                 goto out2;
 268
 269         cdev->owner = fops->owner;
 270         cdev->ops = fops;
 271         kobject_set_name(&cdev->kobj, "%s", name);
 272         for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
 273                 *s = '!';
 274
 275         err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
 276         if (err)
 277                 goto out;
 278
 279         cd->cdev = cdev;
 280
 281         return major ? 0 : cd->major;
 282 out:
 283         kobject_put(&cdev->kobj);
 284 out2:
 285         kfree(__unregister_chrdev_region(cd->major, 0, 256));
 286         return err;
 287 }
 288
 289 void unregister_chrdev_region(dev_t from, unsigned count)
 290 {
 291         dev_t to = from + count;
 292         dev_t n, next;
 293
 294         for (n = from; n < to; n = next) {
 295                 next = MKDEV(MAJOR(n)+1, 0);
 296                 if (next > to)
 297                         next = to;
 298                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 299         }
 300 }
 301
 302 int unregister_chrdev(unsigned int major, const char *name)
 303 {
 304         struct char_device_struct *cd;
 305         cd = __unregister_chrdev_region(major, 0, 256);
 306         if (cd && cd->cdev)
 307                 cdev_del(cd->cdev);
 308         kfree(cd);
 309         return 0;
 310 }
 311
 312 static DEFINE_SPINLOCK(cdev_lock);
 313
 314 static struct kobject *cdev_get(struct cdev *p)
 315 {
 316         struct module *owner = p->owner;
 317         struct kobject *kobj;
 318
 319         if (owner && !try_module_get(owner))
 320                 return NULL;
 321         kobj = kobject_get(&p->kobj);
 322         if (!kobj)
 323                 module_put(owner);
 324         return kobj;
 325 }
 326
 327 void cdev_put(struct cdev *p)
 328 {
 329         if (p) {
 330                 struct module *owner = p->owner;
 331                 kobject_put(&p->kobj);
 332                 module_put(owner);
 333         }
 334 }
 335
 336 /*
 337  * Called every time a character special file is opened
 338  */
 339 int chrdev_open(struct inode * inode, struct file * filp)
 340 {
 341         struct cdev *p;
 342         struct cdev *new = NULL;
 343         int ret = 0;
 344
 345         spin_lock(&cdev_lock);
 346         p = inode->i_cdev;
 347         if (!p) {
 348                 struct kobject *kobj;
 349                 int idx;
 350                 spin_unlock(&cdev_lock);
 351                 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
 352                 if (!kobj)
 353                         return -ENXIO;
 354                 new = container_of(kobj, struct cdev, kobj);
 355                 spin_lock(&cdev_lock);
 356                 p = inode->i_cdev;
 357                 if (!p) {
 358                         inode->i_cdev = p = new;
 359                         inode->i_cindex = idx;
 360                         list_add(&inode->i_devices, &p->list);
 361                         new = NULL;
 362                 } else if (!cdev_get(p))
 363                         ret = -ENXIO;
 364         } else if (!cdev_get(p))
 365                 ret = -ENXIO;
 366         spin_unlock(&cdev_lock);
 367         cdev_put(new);
 368         if (ret)
 369                 return ret;
 370         filp->f_op = fops_get(p->ops);
 371         if (!filp->f_op) {
 372                 cdev_put(p);
 373                 return -ENXIO;
 374         }
 375         if (filp->f_op->open) {
 376                 lock_kernel();
 377                 ret = filp->f_op->open(inode,filp);
 378                 unlock_kernel();
 379         }
 380         if (ret)
 381                 cdev_put(p);
 382         return ret;
 383 }
 384
 385 void cd_forget(struct inode *inode)
 386 {
 387         spin_lock(&cdev_lock);
 388         list_del_init(&inode->i_devices);
 389         inode->i_cdev = NULL;
 390         spin_unlock(&cdev_lock);
 391 }
 392
 393 static void cdev_purge(struct cdev *cdev)
 394 {
 395         spin_lock(&cdev_lock);
 396         while (!list_empty(&cdev->list)) {
 397                 struct inode *inode;
 398                 inode = container_of(cdev->list.next, struct inode, i_devices);
 399                 list_del_init(&inode->i_devices);
 400                 inode->i_cdev = NULL;
 401         }
 402         spin_unlock(&cdev_lock);
 403 }
 404
 405 /*
 406  * Dummy default file-operations: the only thing this does
 407  * is contain the open that then fills in the correct operations
 408  * depending on the special file...
 409  */
 410 struct file_operations def_chr_fops = {
 411         .open = chrdev_open,
 412 };
 413
 414 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 415 {
 416         struct cdev *p = data;
 417         return &p->kobj;
 418 }
 419
 420 static int exact_lock(dev_t dev, void *data)
 421 {
 422         struct cdev *p = data;
 423         return cdev_get(p) ? 0 : -1;
 424 }
 425
 426 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 427 {
 428         p->dev = dev;
 429         p->count = count;
 430         return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 431 }
 432
 433 static void cdev_unmap(dev_t dev, unsigned count)
 434 {
 435         kobj_unmap(cdev_map, dev, count);
 436 }
 437
 438 void cdev_del(struct cdev *p)
 439 {
 440         cdev_unmap(p->dev, p->count);
 441         kobject_put(&p->kobj);
 442 }
 443
 444
 445 static void cdev_default_release(struct kobject *kobj)
 446 {
 447         struct cdev *p = container_of(kobj, struct cdev, kobj);
 448         cdev_purge(p);
 449 }
 450
 451 static void cdev_dynamic_release(struct kobject *kobj)
 452 {
 453         struct cdev *p = container_of(kobj, struct cdev, kobj);
 454         cdev_purge(p);
 455         kfree(p);
 456 }
 457
 458 static struct kobj_type ktype_cdev_default = {
 459         .release        = cdev_default_release,
 460 };
 461
 462 static struct kobj_type ktype_cdev_dynamic = {
 463         .release        = cdev_dynamic_release,
 464 };
 465
 466 struct cdev *cdev_alloc(void)
 467 {
 468         struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 469         if (p) {
 470                 memset(p, 0, sizeof(struct cdev));
 471                 p->kobj.ktype = &ktype_cdev_dynamic;
 472                 INIT_LIST_HEAD(&p->list);
 473                 kobject_init(&p->kobj);
 474         }
 475         return p;
 476 }
 477
 478 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 479 {
 480         memset(cdev, 0, sizeof *cdev);
 481         INIT_LIST_HEAD(&cdev->list);
 482         cdev->kobj.ktype = &ktype_cdev_default;
 483         kobject_init(&cdev->kobj);
 484         cdev->ops = fops;
 485 }
 486
 487 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 488 {
 489         if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
 490                 /* Make old-style 2.4 aliases work */
 491                 request_module("char-major-%d", MAJOR(dev));
 492         return NULL;
 493 }
 494
 495 void __init chrdev_init(void)
 496 {
 497         cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 498 }
 499
 500
 501 /* Let modules do char dev stuff */
 502 EXPORT_SYMBOL(register_chrdev_region);
 503 EXPORT_SYMBOL(unregister_chrdev_region);
 504 EXPORT_SYMBOL(alloc_chrdev_region);
 505 EXPORT_SYMBOL(cdev_init);
 506 EXPORT_SYMBOL(cdev_alloc);
 507 EXPORT_SYMBOL(cdev_del);
 508 EXPORT_SYMBOL(cdev_add);
 509 EXPORT_SYMBOL(register_chrdev);
 510 EXPORT_SYMBOL(unregister_chrdev);